Noob question. I have an '05 tc, and when I bought it at the dealership, they placed 18" gt sport rims on them. Its 5 years now and I really only use my tC to get from point A to B, but I'd like to change the tires & wheels in one purchase.

I've read the Sticky (http://www.scionlife.com/forums/showthread.php?t=142934)on Fitment, but being that I've never changed or bought tires before, I was at a loss.
(http://www.scionlife.com/forums/showthread.php?t=142934)
I'm downgrading, going to 17" rims (wasn't that the stock size?). Anyways the wheels I'm set on are
(17X7 5-100/114 42SM).

I've spent the past 2 hours trying to figure out (google) how to match the right tire specifications, but so far nothing.

Do you have advice on to figure out how figure out the tire specs that would match? So far, one tire shop was recommending specs of (215/45R-17 87H VSB), but that was for the default wheels, and I wasn't sure if that would match the new wheels I've chosen (17X7 5-100/114 42SM).

any 215/45/17 will fit those rims like a glove.

any 215/45/17 will fit those rims like a glove.

Ty for the response - placed those specs @ a local tire shop and found a set of 4 tires to go with the new rims.

Quick follow-up though, how do u calculate or correlate the tire specs with the wheel specs? The only corresponding # was the 17, and I understand thats for the diameter of the wheels - but where do the 215 and 45 come from?

Tires are broken out by width, sidewall height, overall diameter. So when you see something like 215/45/17 it's actually something like 215mm wide, 45mm sidewall height, 17inches overall diameter.

Using THIS (http://www.bing.com/search?q=tire+size+calculator&src=IE-SearchBox&Form=IE8SRC)search, you can get to Kouki.co.uk (http://www.kouki.co.uk/utilities/visual-tyre-size-calculator) which has a nifty little tire size calculator. There are plenty of sites out there for this type of stuff, but Kouki has a good visual output to show you the differences.

If you need to know what size tire fits what size rim, it's usually best to ask your local tire shop. They can just check their databases to see the range of tires that fit the size rims you're looking at. Otherwise, Rangerryda was spot-on with his suggestion. If you're curious about tires for future purchases take a look at the links (and other resources) and keep up the good work with researching/asking questions. :)